No longer run Rust classes inside Godot editor

[Bromeon]

Closes #70.
Closes #132.

Raises MSRV from 1.66 to 1.70.

So far, the workaround to prevent Rust classes from running in the editor was:

if Engine::singleton().is_editor_hint() {
    return;
}

With this PR, this is no longer necessary. By default, all virtual callbacks (ready, process etc.) are no longer invoked.
Note that classes will still be registered (this is necessary as scene trees would be broken otherwise).

This is still quite rudimentary and can be refined over time, but it should already improve the user experience.

The old behavior -- which may be desired by plugins/extensions rather than games -- can be restored with a configuration in the init trait:

#[gdextension]
unsafe impl ExtensionLibrary for DodgeTheCreeps {
    fn editor_run_behavior() -> EditorRunBehavior {
        EditorRunBehavior::Full
    }
}

See API Docs for more information.

[GodotRust]

API docs are being generated and will be shortly available at: https://godot-rust.github.io/docs/gdext/pr-365

[Bromeon]

Merging since I need the changes for follow-up work, but feel free to leave feedback!

[kulkalkul]

I figured game classes also benefit from running inside editor, occasionally. I think them similar to how @tool scripts work in gdscript. Might not worth the hussle, but having a way to register classes as "tool classes" and allowing them to run in editor might be preferable to Full vs. NoVirtuals in some places.

[Bromeon]

Yep, I was considering per-class as well (also why I made the behavior an enum and not bool).

One possibility would be something like this:

#[derive(GodotClass)]
#[class(init, base=Node, tool)]
struct MyClass {
    ...
}

And then the global config:

#[gdextension]
unsafe impl ExtensionLibrary for DodgeTheCreeps {
    fn editor_run_behavior() -> EditorRunBehavior {
        EditorRunBehavior::ToolsOnly
    }
}

Probably this should be the default.

Under that design, would it even be useful to have EditorRunBehavior::NoVirtuals (i.e. everything off)?

[kulkalkul]

Yeah, that would be perfect!

Under that design, would it even be useful to have

I don't think so. No real usecase came into my mind

[Bromeon]

@kulkalkul "tool classes" are implemented in #374.

[kulkalkul]

Yeah, that's way better, thanks!